Robust nose torque-limiting device

ABSTRACT

A torque-limiting driver has a handle, a body, a torque-limiting assembly and a work-piece engaging tip. The torque-limiting assembly includes an upper and lower shank that have a plurality of teeth circumferentially spaced. The teeth have a vertical face, an inclined face, and a flat peak. There is a spring for applying pressure across the upper and lower shank with multiple washers interposed between the lower shaft and spring. In some instances, there is a round square drive with arched catches having preselected radii to assure operation over certain cycles at selected torque and to reduced nose cone damage and breakage at a predetermined inch pounds of torque.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/191,203, filed Jul. 26, 2011, and claims the benefit of and priorityto U.S. Provisional Applications Ser. No. 61/463,548 with a filing dateof Feb. 19, 2011 and 61/368,519 with a filing date of Jul. 28, 2010, allof which are incorporated as if fully set forth herein in theirentirety.

BACKGROUND

1. Field

This disclosure relates to a medical use driver tool and, in particular,to a torque-limiting driver that disengages at a predefined torquelimit.

2. General Background

Torque-limiting drivers are widely used throughout the medical industry.These torque-limiting drivers have a factory pre-set torque to ensurethe accuracy and toughness required to meet a demanding surgicalenvironment.

The medical industry has made use of both reusable and disposabletorque-limiting drivers. In a surgical context, there is little room forerror and these drivers must impart a precise amount of torque.

Reusable drivers require constant recalibration to ensure that thedriver is imparting the precise amount of torque. Recalibration is acumbersome task but must be done routinely.

Disposable drivers are an easy to use and reliable alternative to thereusable drivers. Typically, a medical device such as an implant, forexample, is packaged with a disposable driver designed to the implant'sspecifications. Once the driver has been used, it can be discarded.Thus, a surgeon can have complete confidence that the disposable driver,packaged with an implant, will impart the precise amount of torque.Typically, the torque requirement is different for different operationsand for different implants. For example, applications may include thosein the field of orthopedic surgery, construction and emplacement ofimplants, etc.

These disposable drivers have been used for low torque applications. Thestandard torque values in these applications typically range from 4 to20 inch-ounces. It has, however, been a challenge to develop a reliabledisposable driver capable of imparting higher torques for largerapplications.

Disclosure

Torque is a measure of how much force acting on an object causes thatobject to rotate. In the case of a driver and a fastener, thismeasurement can be calculated mathematically in terms of the crossproduct of specific vectors:τ=r×F

Where r is the vector representing the distance and direction from anaxis of a fastener to a point where the force is applied and F is theforce vector acting on the driver.

Torque has dimensions of force times distance and the SI unit of torqueis the Newton meter (Nm). The joule, which is the SI unit for energy orwork, is also defined as an Nm, but this unit is not used for torque.Since energy can be thought of as the result of force times distance,energy is always a scalar whereas torque is force cross-distance and sois a vector-valued quantity. Other non-SI units of torque includepound-force-feet, foot-pounds-force, ounce-force-inches,meter-kilograms-force, inch-ounces or inch pounds.

A disposable torque-limiting driver, in accordance with the presentdisclosure, has a handle, a cylindrical body and a work-piece engagingtip. Within the cylindrical body there is a torque-limiting assembly.The torque-limiting assembly includes an upper cylindrical shank and alower cylindrical shank. The upper cylindrical shank and the lowercylindrical shank have a plurality of teeth. The teeth have a verticalface, an inclined face and a substantially flat peak. The inclined faceis defined by a first radius of curvature that transitions to thesubstantially flat peak. The teeth are spaced circumferentially andspiral around the upper cylindrical shank and a lower cylindrical shank.There is a spring for applying pressure across the upper cylindricalshank and the lower cylindrical shank. The teeth of the uppercylindrical shank and the lower cylindrical shank engage for relativerotation when the handle is turned and disengage when a predeterminedvalue of torque is exceeded.

Smooth repeat operation is encouraged with specific dual bearingsurfaces.

A round square implementation provides a range of use over predeterminedcycles of up to almost 150 inch pounds rotations without cracking theplastic nose cone. In some instances a square engagement with radiusescorners having radii between about 0.1482 and about 0.1638 inches areoptimal. In some instances a square engagement with radiuses cornershaving radii between about 0.1292304 and about 0.1716 inches areoptimal. In other instances a square engagement with radiuses cornershaving radii is between about 0.1266 and about 0.1794 inches is optimal.

A torque driver capable of transferring high torque with a spring havinga spring constant (also referred to as a force constant) which exerts agreater force in an initial (rest) state via a multiple washer bearinginterface. A single washer interface with end of spring may have atendency to grip or bind spring and washer; a multiple washer interfaceprovides a bearing surface between spring and remote second washer.Elimination or reduction of binding or gripping between washer andspring may provide a smoother rotation.

DRAWINGS

FIG. 1 is a perspective view of a driver in accordance with the presentdisclosure.

FIG. 2 is an exploded view of a driver in accordance with the presentdisclosure.

FIG. 3 is a vertical cross sectional view of a driver in accordance withthe present disclosure.

FIG. 4 is a horizontal cross sectional view of a driver in accordancewith the present disclosure.

FIG. 5 is a perspective view of an upper shank in accordance with thepresent disclosure.

FIG. 6 is a profile of a tooth from a clutch assembly in accordance withthe present disclosure.

FIG. 7 is a perspective view of the teeth from a clutch assembly inaccordance with the present disclosure.

FIG. 8 is a top view of the teeth from a clutch assembly in accordancewith the present disclosure.

FIG. 9 is a partial exploded view of the nose region of FIG. 2.

FIG. 10 is an exploded view of a driver in accordance with the presentdisclosure.

FIG. 11 is shaft in accordance with the present disclosure.

FIG. 12 is a cross sectional view at line A-A of FIG. 11 in accordancewith the present disclosure.

FIG. 13 is a front view of the nose of FIG. 10 in accordance with thepresent disclosure.

FIG. 14 shows test results with a driver having a triangular geometry.

FIG. 15 shows test results with a driver having a hex geometry.

FIG. 16 shows test results with a driver having a round square geometry.

FIG. 17 shows test results of round square configurations with about 13revolutions using a single washer.

FIG. 18 shows test results of round square configurations with about 11revolutions using two adjacent washers.

While the specification concludes with claims defining the features ofthe present disclosure that are regarded as novel, it is believed thatthe present disclosure's teachings will be better understood from aconsideration of the following description in conjunction with theappendices, figures, in which like reference numerals are carriedforward. All descriptions and callouts in the Figures and Appendices arehereby incorporated by this reference as if fully set forth herein.

Further Disclosure

Referring to FIGS. 1-9, there is a torque-limiting driver 100. Thetorque-limiting driver 100 has a generally T-shaped handle. The T-shapedhandle includes arms 4 at one end an axially extending generally hollowcylindrical body 6, a cap 2 that covers the same end of the T-shapedhandle and a cylindrical end 18 opposite the T-shaped handle on thecylindrical body 6. The cap 2 may be snap-fitted to the cylindrical body6, or may be welded, or attached by any equivalent thereof and the bodyis preferably molded from a plastic or other economical equivalents.

At the cylindrical end 18, there is a lower shank 700 that has andannularly tapering body and a nose cone 8 along its length. The lowershank 700 may have a plurality of support flanges 10 that add strengthwhile saving material. At one end, the lower shank 700 tapers to a drivesocket 9 at the end of the nose cone 8 molded to engage a shaft 14. Theshaft 14 maybe substantially linear with a proximal end that mates withsaid drive socket. The shaft 14 may be hexagonal or cylindrical intransverse cross-sectional shape and is provided, at one end, with awork piece-engaging distal tip 12, adapted for engagement with anassociated work-piece, such as a fastener or the like. The workpiece-engaging distal tip 12 is shown to be a hex wrench, but could be ascrewdriver, wrench, or any other tool or medical tool arrangement. Atan opposite end, the lower shank 700 has a plurality of teeth 82arranged in a crown gear formation, a circumferential rim 31 extendingradially outwardly and an internally threaded axial bore.

FIG. 2 is an exploded view of the driver 100. Inside the cylindricalbody 6 a clutch assembly is disposed. The clutch assembly includes anupper shank 800 for forcibly engaging the lower shank 700. The uppershank 800 has a bottom face that has teeth 82 arranged in a crown gearformation and an annular flange or circumferential rim 83 extendingradially outwardly. Shown on FIG. 5, the upper shank 800 includes anannular body or outer cylindrical shank 84, an axial bore 92 through aninner shank 86. The inner shank 86 and outer shank 84 are connected viainner supports 88, leaving the upper shank 800 substantially hollow withinternal spaces 90 on a top face.

The upper shank 800 also includes at least one recess 80 on the side ofthe outer shank. The recess 80 is provided as a cylindrical cut, reliefor recess into the side of the outer shank and maybe provided as asquare or rectangular cut or the cut may have a slanted side or sidesrelative to the axis of the upper shank 800 as shown in FIG. 2.

In assembly, the shaft 14 at its proximal end forms drive connection 16which is received into the drive socket 9 of the lower shank 700. Awasher (not detailed in the implementation) may be provided between thecircumferential rim 31 of the lower shank 700 and a circumferentialflange 30 extending radially inward within the hollow of the cylindricalbody 6. Alternatively, the circumferential rim 31 of the lower shank 700may be provided flush against circumferential flange 30 of thecylindrical body 6.

Drive socket 9 and the connection 16 are shown having correspondingcross sectional shape. In this implementation the hexagonal shapeprovides multiple stops and surface area to facilitate consistentoperation over the anticipated use profile without significant wiggle orloosening of the shaft 14 from the drive socket 9. A use profileincludes, but is not limited to, such factors as required lbf (load) orinch pounds of torque, number of uses, cycle time, material nose cone 8is formed of and material forming shaft 14.

The opposite side of the circumferential flange 30 receives thecircumferential rim 83 of the upper shank 800 allowing the teeth 82 ofthe lower shank 700 to engage the teeth 82 of the upper shank 800 when atorque is applied.

Integrally formed within the cylindrical body 6, a protrusion 85 mateswith the recess 80 of the upper shank 800. FIG. 3 and FIG. 4 are crosssectional views that best illustrate the protrusion 85 in relation withthe recess 80. The protrusion 85 extends inward in a radial fashion andhas a length along the axis of the cylindrical body 6 for relativemoveable engagement within the recess 80. This engagement provides alocking mechanism of the shaft 14 relative to the T-shaped handle viathe upper shank when pressure is applied across the lower shank 700 andthe upper shank 80. The recess 80 is provided circumferentially widerthan the protrusion 85 for allowing the cylindrical body 6 and theT-shaped handle to rotate in reverse a predetermined distance from alocked position without subsequent reverse rotation of the workpiece-engaging tip 12. Thus, the at least one recess 80 and at least oneprotrusion 85 lock the T-shaped in one direction providing the necessarytorque to drive a fastener and allow for a predetermined amount ofreverse rotation before unscrewing the fastener.

Force is applied across the lower shank 700 and the upper shank 800 viaa spring 22 within the cylindrical body 6. Inside the cylindrical body6, shown in FIG. 2 and FIG. 5, a washer 20 is provided between the uppershank 800 and the spring 22. The washer transfers pressure from thespring 22 over the top face of the upper shank 800. At an end of thespring 22 opposite the upper shank 800, a cup washer 24 and a lockingfastener 26 hold the spring 22 in a compressed state. The lockingfastener 26A has a fastener head 26B and has a threading 28 that engagesa complementary threading within an axial bore 72 of the lower shank700. Thus, imparting pressure between the respective teeth 82 of thelower shank 700 and the upper shank 800. The spring 22 and the lockingfastener 26A provide the proper tensioning and biasing for the clutchassembly and, generally, the locking fastener 26A is adjustable toprovide proper tension and calibration.

Formed on the top face of the lower shank 700 and the bottom face of theupper shank 800 are the plurality of teeth 82 that forcibly engage toimpart torque from the T-shaped handle to the work piece when a torqueis applied. Referring to FIGS. 6-7, tooth 82 has an inclined face 66that smoothly transitions to a substantially flat peak 60, via a firstradius of curvature 64. The substantially flat peak 60 subsequentlytransitions smoothly, via a second radius of curvature, to a verticalface 68 that is substantially parallel to the axis of the lower shank700 and the upper shank 800. The first radius of curvature is typicallymuch larger than the second radius of curvature.

Experimental results have shown that a tooth having an inclined facethat smoothly transitions to a substantially flat face is capable ofimparting a substantial increase in torque to a fastener. In oneexperiment, a ten-fold increase in torque was observed. This increase intorque is due to the frictional forces associated with the smoothlytransitioning curve of an inclined face 66 of the teeth 82.

In a simplified example, when two uniform inclines are frictionallyengaged, only one static force, having a single coefficient of staticforce, is acting against the relative movement of the two inclines.However, when the two inclines are not uniform, more than onecoefficient of static force can be observed, thus resulting in a higherdisinclination to movement.

The teeth 82 are circumferentially spaced in a crown gear formation ofthe top face and bottom face of the lower shank 700 and the upper shank800 respectively. The teeth 82 are also preferably configured in aspiral formation, best shown in FIG. 7. Each face of the lower shank 700and the upper shank 800 has an inner radius and an outer radius and theteeth 82 spiral around the inner radius resulting in a larger toothdetail when viewing the tooth from the outer radius relative to thetooth detail when viewing the tooth from the inner radius. The spiralconfiguration of the teeth 82 can also be defined as having a longerinclined face 66 at the edge of the tooth on or near the outer radiusrelative to the inclined face 66 at the edge of the tooth on or near theinner radius of the lower shank 700 and the upper shank 800. Resultshave shown that teeth arranged in a spiral configuration provide anincreased reliability and precision in torque consistency when comparedto their non-spiral counterparts.

The substantially flat peak 60 of the teeth 82 can be as wide at theinner radius as they are at the outer radius. Alternatively, thesubstantially flat peak 60 may be wider at the outer radius and tapertoward the inner radius.

The vertical faces 68 of the teeth 82 of the lower shank 700 and theupper shank 800 respectively engage when a torque is applied to preventrelative rotation of the lower shank 700 and the upper shank 800 in onedirection. The inclined faces 66 engage to accommodate relative rotationof the lower shank 700 and the upper shank 800 in an opposite direction.

The extent to which the locking screw 26 is threaded into the axial bore72 of the lower shank 700 controls the amount of compression or preloadon the spring 22 which, subsequently, controls the limiting torquerequired to effect relative rotation of the lower shank 700 and theupper shank 800. If the locking screw 26 is threaded deeply into thelower shank 700, a higher torque will be required to disengage the teeth82 of the lower shank 700 and the upper shank 800 than if locking screw26 was threaded into the lower shank 700 relatively shallow.

Thus, when the driver 100 is rotated in one direction, the shaft 14 willrotate with the cylindrical body 6 and T-shaped handle until apredetermined torque is reached. When this predetermined torque isreached, a biasing force exerted by the spring 22 is overcome, allowingan inclined face 66 of the upper shank 800 to slide up a respectiveinclined face 66 of the lower shank 700, subsequently snapping the teeth82 of the lower shank 700 into engagement behind a next tooth of theupper shank 800. This snapping sound is typically an audible indicationto a user that a predetermined torque has been reached.

When a force beyond the required value of torque is reached, the teethof the lower shank 700 and the upper shank 800 will continue todisengage, resulting in rotation of the handle with no further rotationof the work piece-engaging tip 12. Thus, the handle will continue torotate, disengaging the teeth 82 with every rotational movement thatwill not impart continued force beyond a predefined threshold to thefastener.

When the driver 100 is rotated in the opposite direction, the T-shapedhandle rotates in reverse a predetermined distance from a lockedposition without subsequent reverse rotation of the work piece-engagingtip 12. However, when the protrusion 85 travels the predetermineddistance and locks against the opposite end of the recess 80, the driver100 will operate as a standard driver with no torque-limiting featuresince the engaging vertical face 68 will force relative rotation of thelower shank 700 and the upper shank 800 in the opposite directionwithout any torque-limiting feature.

The disposable torque-limiting driver of the present disclosurepreferably imparts torques on the order of about 1 ounce inch to 100inch ounces. Torques of this magnitude can be utilized in precision hightorque environments such as the installation of dental, joint, vertebralimplants and the like. Typically, the torque requirement is differentfor different operations and for different implants. Therefore, in someinstances, the torques maybe around 1 inch pounds. In other instances,the predetermined torque maybe at least 30 inch pounds and yet otherinstances, at least 60 inch pounds, depending on an implant'sspecifications.

In some instances, a torque-limiting driver, such as driver 100, may beprepackaged with an implant provided for one-time use. Such an instanceinsures that the driver imparts the required amount of torque and hasnot been worn in or dulled by overuse.

In other instances, the driver 100 may be reusable. The shaft 14 may beinterchangeably fixed relative to the nose cone 8 for the accommodationof multiple work piece engaging tips 12. It is also to be appreciatedthat the handle of the driver is not limited to a T-shape and may beprovided in any other suitable configuration.

Referring to FIGS. 10-13, there is a torque-limiting driver 200. Thetorque-limiting driver 200 generally includes a handle. The handle 2includes arms 4 at one end an axially extending generally hollowcylindrical body 6, a cap 2 that covers the same end of the T-shapedhandle and a cylindrical end 18 opposite the T-shaped handle on thecylindrical body 6. The cap 2 may be snap-fitted to the cylindrical body6, or may be welded, or attached by any equivalent thereof and the bodyis preferably molded from a plastic or other economical equivalents.

At the cylindrical end 18, there is a lower shank 700 that has andannularly tapering body and a nose cone 8 along its length. The lowershank 700 may have a plurality of support flanges 10 that add strengthwhile saving material. At one end, the lower shank 700 tapers to anaxial drive socket 9′ at the end of the nose cone 8 molded of anon-metal material such as a plastic, polymer, resin including but notlimited to (plastics, resins, polymers, imides, fluoropolymers,thermoplastic polymers, thermosetting plastics, and the like as well asblends or mixtures thereof) to engage a shaft 14. The shaft 14 driveconnection 16′ is rounded square in transverse cross-sectional shape(see FIGS. 11 and 12) and is provided, at one end, with a workpiece-engaging tip 12. The shaft 14 is substantially round in crosssection. The drive connection 16′ is generally square but has roundedcorners 95 connecting substantially flat sides 97. Testing hasdemonstrated that eliminating hard corners between the walls of thesquare cross section drive connection 16′ to the drive socket 9′ oflower shank 700 more evenly distributes the force applied thereto andsubstantially reduces, deformation, bending, breaking, and/or crackingof the non-metal nose cone 8 region of the drive socket 9′ at high load(lbf) and/or inch pounds over time as compared to other geometries ofdrive socket and drive connection as shown in FIGS. 14-16.

In some implementations the round square implementation provides a rangeof use over predetermined cycles of up to almost 150 inch pounds. Insome implementations the round square implementation provides a range ofuse over predetermined cycles of between at least about 10 and about 140inch pounds. In addition testing has shown that the round square crosssection of the drive connection 16′ and drive socket 9′ have a morerobust connection, compared to, triangle or hexagonal and does not“strip”, deform or spin in the drive socket as readily as shafts anddrive sockets with hexagonal or triangular cross sections. Within thecorresponding drive socket 9′, as shown in FIG. 13 the radii of about0.156 inches of the catches 99 correspond to the rounded corners 95 ofthe drive connection 16′. Within the drive socket 9′ of the nose 8 isgenerally square but has rounded corners 95 connecting substantiallyflat sides 97. The drive socket 9′ in cross section has foursubstantially planar walls; four arched corners (the catches 99) andeach catch 99 with a preselected radius to distribute the load caused byturning shaft 14 at a predetermined torque over a predetermined numberof rotations without cracking the plastic nose cone 8 material thatsurrounds the drive socket to a point of failure. The optimal range ofradii to achieve even (as in even load) repetitive rotations can beselected to correspond to the torque requirements of a particulardriver. In some implementations the optimal radii is between about0.1482 and about 0.1638 inches. In some implementations the optimalradii is between about 0.1292304 and about 0.1716 inches. In someimplementations the optimal radii is between about 0.1266 and about0.1794 inches.

At an opposite end, the lower shank 700 has a plurality of teetharranged in a crown gear formation, a circumferential rim 31 extendingradially outwardly and an internally threaded fastener bore.

FIG. 10 is an exploded view of the driver 200. Inside the cylindricalbody 6 a clutch assembly is disposed. The clutch assembly includes anupper shank 800 for forcibly engaging the lower shank 700. The uppershank 800 has a bottom face that has teeth arranged in a crown gearformation and an annular flange or circumferential rim extendingradially outwardly.

According to aspects of one or more exemplary implementations, force isapplied across lower shank 700 and upper shank 800 via spring 22 withincylindrical body 6. Inside cylindrical body 6, shown in FIG. 10 washer20 and washer 21 are provided between upper shank 800 and spring 22.Washer 20 and washer 21 transfer pressure from spring 22 over the topface of upper shank 800. At an end of spring 22 opposite upper shank800, shoulder washer 25 and a fastener 26A fastener head 26B hold spring22 in a relatively compressed state. Washer between shoulder washer 25and spring 22 to facilitate relative rotation of fastener head 26 andspring 22. The fastener is threaded 28 and said threads engage with theinternally threaded fastener bore inside of the lower shank 700.

According to aspects of one or more exemplary implementations, driver200 capable of transferring higher torque may be provided with spring 22having a greater spring constant (i.e., force constant) or otherwise becalibrated with spring 22 exerting greater forces in an initial (rest)state. A more robust spring 22 may be used when adding washer 20 andwasher 21 at the end of said spring nearest said upper shank 800, insuch instance although spring 22 may have a tendency to grip relative towasher 21 the bearing surface between washer 20 and washer 21 providesfor smooth rotation. FIGS. 17-18 provide test results showing that anincreased load may be achieved when using a multi-washer (21 and 20)system as opposed to a single washer (20 or 21). In some implementationsdisclosed is a drive socket 9′ which in cross section has foursubstantially planar walls; four arched corners (the catches 99) andeach catch 99 with a preselected radius to distribute the load caused byturning shaft 14 at a predetermined torque over a predetermined numberof rotations without cracking or otherwise damaging the non-metal nosecone 8 material that surrounds the drive socket to a point of failure. Amore robust spring 22 increases the probability of a friction griprelative to washer 21. Provision of additional washer 20 preserves atleast one free-spinning structure between the distal end of the spring22 and upper shank 800. At the proximal end of the spring the shoulderwasher 27 and washer 25 replace the cup washer 24. testing shows that acup washer, such as that shown in FIGS. 2 and 3 may over time deform,indent, bend, break fail or partially fail from use and the pressureexcreted thereon by the fastener head 26B against the cup washer 24. Theshoulder washer 27 fastener head 26B interaction reduce such failure ordeformation.

In assembly, drive connection 16′ of shaft 14 is received into drivesocket 9′ of lower shank 700. Washer 32 maybe provided betweencircumferential rim 31 of lower shank 700 and circumferential flange 30extending radially inward within the hollow of cylindrical body 6.Washer 32 may be of a polymer or other material having low coefficientof friction. Alternatively, circumferential rim 31 of lower shank 700may be provided flush against circumferential flange 30 of cylindricalbody 6.

While the method and agent have been described in terms of what arepresently considered to be the most practical and preferredimplementations, it is to be understood that the disclosure need not belimited to the disclosed implementations. It is intended to covervarious modifications and similar arrangements included within thespirit and scope of the claims, the scope of which should be accordedthe broadest interpretation so as to encompass all such modificationsand similar structures. The present disclosure includes any and allimplementations of the following claims.

It should also be understood that a variety of changes may be madewithout departing from the essence of the disclosure. Such changes arealso implicitly included in the description. They still fall within thescope of this disclosure. It should be understood that this disclosureis intended to yield a patent covering numerous aspects of thedisclosure both independently and as an overall system and in bothmethod and apparatus modes.

Further, each of the various elements of the disclosure and claims mayalso be achieved in a variety of manners. This disclosure should beunderstood to encompass each such variation, be it a variation of animplementation of any apparatus implementation, a method or processimplementation, or even merely a variation of any element of these.

Particularly, it should be understood that as the disclosure relates toelements of the disclosure, the words for each element may be expressedby equivalent apparatus terms or method terms—even if only the functionor result is the same.

Such equivalent, broader, or even more generic terms should beconsidered to be encompassed in the description of each element oraction. Such terms can be substituted where desired to make explicit theimplicitly broad coverage to which this disclosure is entitled.

It should be understood that all actions may be expressed as a means fortaking that action or as an element which causes that action.

Similarly, each physical element disclosed should be understood toencompass a disclosure of the action which that physical elementfacilitates.

Any patents, publications, or other references mentioned in thisapplication for patent are hereby incorporated by reference. Inaddition, as to each term used it should be understood that unless itsutilization in this application is inconsistent with suchinterpretation, common dictionary definitions should be understood asincorporated for each term and all definitions, alternative terms, andsynonyms such as contained in at least one of a standard technicaldictionary recognized by artisans and the Random House Webster'sUnabridged Dictionary, latest edition are hereby incorporated byreference.

Finally, all referenced listed in the Information Disclosure Statementor other information statement filed with the application are herebyappended and hereby incorporated by reference; however, as to each ofthe above, to the extent that such information or statementsincorporated by reference might be considered inconsistent with thepatenting of this/these disclosure(s), such statements are expressly notto be considered as made by the applicant(s).

In this regard it should be understood that for practical reasons and soas to avoid adding potentially hundreds of claims, the applicant haspresented claims with initial dependencies only.

Support should be understood to exist to the degree required under newmatter laws—including but not limited to United States Patent Law 35 USC132 or other such laws—to permit the addition of any of the variousdependencies or other elements presented under one independent claim orconcept as dependencies or elements under any other independent claim orconcept.

To the extent that insubstantial substitutes are made, to the extentthat the applicant did not in fact draft any claim so as to literallyencompass any particular implementation, and to the extent otherwiseapplicable, the applicant should not be understood to have in any wayintended to or actually relinquished such coverage as the applicantsimply may not have been able to anticipate all eventualities; oneskilled in the art, should not be reasonably expected to have drafted aclaim that would have literally encompassed such alternativeimplementations.

Further, the use of the transitional phrase “comprising” is used tomaintain the “open-end” claims herein, according to traditional claiminterpretation. Thus, unless the context requires otherwise, it shouldbe understood that the term “compromise” or variations such as“comprises” or “comprising”, are intended to imply the inclusion of astated element or step or group of elements or steps but not theexclusion of any other element or step or group of elements or steps.

Such terms should be interpreted in their most expansive forms so as toafford the applicant the broadest coverage legally permissible.

The matter set forth in the foregoing description and accompanyingdrawings is offered by way of illustration only and not as a limitation.While particular embodiments have been shown and described, it will beapparent to those skilled in the art that changes and modifications maybe made without departing from the broader aspects of applicants'contribution. The actual scope of the protection sought is intended tobe defined in the following claims when viewed in their properperspective based on the prior art.

The invention claimed is:
 1. A method of reducing plastic nose conebreakage of a disposable torque-limiting driver operating at a selectedtorque, the method comprising: applying a preselected amount of torqueto a tool fitted to a torque limiting device via a drive socket of aplastic nose section; said drive socket having been formed of foursubstantially planar walls and interposed between each wall is an archedcorner catch each with a radius configured to distribute the forcecaused by turning a shaft at the predetermined torque without crackingthe plastic nose cone over a predetermined number of rotations; whereinthe predetermined torque is at least 60 inch pounds; wherein the nosecone continues to function within the predetermined torque range for atleast about 105 cycles; and wherein the radius is between 0.1266 inchesand 0.1794 inches.
 2. The method of claim 1 wherein the predeterminedtorque is between about 75 inch pounds and about 85 inch pounds.
 3. Themethod of claim 2 wherein the nose cone continues to function within thepredetermined torque range for at least about 108 cycles.
 4. The methodof claim 2 wherein the nose cone continues to function within thepredetermined torque range for at least about 138 cycles.
 5. The methodof claim 1 the predetermined torque is between about 105 inch pounds andabout 110 inch pounds.
 6. The method of claim 5 wherein the nose conecontinues to function within the predetermined torque range for at leastabout 135 cycles.
 7. The method of claim 1 the predetermined torque isabove about 120 inch pounds.
 8. The method of claim 7 wherein the nosecone continues to function within the predetermined torque range for atleast about 135 cycles.
 9. The method of claim 1, wherein the radius isbetween 0.1482 inches and 0.1638 inches.
 10. The method of claim 1,wherein the radius is between 0.1292304 inches and 0.1716 inches.